Electronic Coin Changer Control Circuit

Abstract

A coin changer control circuit has three separate logic input sections individually representing nickels, dimes, quarters, and any other coins or tokens which may be used in a vending machine or the like. A system clock is driven responsive to the usual 60 Hertz (or any other convenient frequency) of commercial power. Each logic input section gates out a selected number of clock pulses representing the monetary value of each deposited coin. A register stores the gated pulses as they are received and then the system compares the price of a vended product with the number of gated pulses to enable or inhibit the vending cycle of the machine. If present, certain undesired vending functions (such as a jammed coin, changer empty, or the like) are also inserted into the comparator to create an inhibit function. However, once the vend cycle begins, it seizes control over the system and prevents a malfunction resulting from changing conditions which may occur during a vend cycle.

Description

This invention relates to change-making apparatus and especially -- although not exclusively -- to electronic change-making control circuits for all sizes of vending machines.

Vending machines are rapidly coming into general use for distribution of many different kinds of products having a great variety of prices. Moreover, with the continuous changing of products and rising prices, it is often necessary to change the price of vended products.

These machines have traditionally had mechanical structures in them for controlling change-making devices. However, these structures become very complicated and, therefore, expensive. While they have functioned well for dispensing fixed price products (such as candy bars, cigarettes, etc.), they are too complex to be easily reset, especially when they dispense products where the prices change often or where there is a wide spread of prices.

Mechanical changers are less than desirable because the vending machines are becoming larger and more versatile. For example, some of the newer machines may vend in the order of forty or more different products. The problems of mechanical linkage between forty or so different controls become too complex to solve easily. Thus, the industry tends to be restrained from further development.

Still another factor is that electronic components are becoming progressively less expensive while mechanical components cannot enjoy any further cost reduction. Thus, the price per transistor drops as production techniques improve while the price of a metal linkage bar goes up as material prices increase. The assemblage of gears, cams, bars, nuts, bolts and the like is a labor-intensive task which becomes more expensive as wage rates go up. The assemblage of electronic components is adaptable to automated production.

Hence, there is a pressing need for new and improved electronic controls to replace mechanical controls. However, this replacement is not a simple task. The electronic controls are subject to environmental constraints, and vending machines are likely to be installed almost anywhere, such as near flashing signs, powered tools, appliances and other sources of electrical noise. Also, the scale of production enters into the design consideration. Some vending machines are produced in small volume relative to an electronic scale of economy. For example, it may not be economically feasible to produce a complex integrated circuit chip when the production demand is for only ten vending machines per week.

Thus, it is seen that many problems must be overcome in order to provide an electronic control circuit for a vending machine.

Accordingly, an object of this invention is to provide new and improved controls for coin changers. Here an object is to provide such control circuits for use in hostile environments. In particular, an object is to provide control circuits which are immune to malfunctions responsive to nearby noise generators.

Another object of the invention is to provide control circuits for vending machines. Here an object is to enable vending machines to dispense products having any of a great variety of different prices and to accept almost any combination of coins, giving the required change if there is an overpayment. More particularly, an object is to provide control circuits which conform to generally accepted business practices of the vending machine industry. These practices include such things as lock up responsive to a jammed coin, restrict the change on any transaction to a particular maximum number of coins per vend cycle, and lock out all except exact change purchases when the number of coins available for change falls to this maximum, force the delivery of a full amount of change once the vend cycle begins, etc.

Still another object of this invention is to provide the foregoing and other objects at an economically attractive cost. Here an object is to provide a coin changer control circuit which has a low cost, even at low volume. Another object is to provide a coin changer control circuit which is compatible with a fully electronic vending machine.

Still other objects will readily occur to those who are skilled in the art.

In keeping with an aspect of the invention, these and other objects are accomplished by a coin changer control circuit having three separate logic input sections representing nickels, dimes, and quarters, for example. A system clock is driven responsive to the usual 60 Hertz of commercial power. Each logic input control section gates out a selected number of clock pulses representing the monetary value of each deposited coin. A register stores the gated pulses. Thereafter, the system compares the cumulative value of stored pulse with the price of a vended product to either enable or inhibit the vending cycle. Certain undesired vending functions (such as a jammed coin, changer empty, or the like) may also be inserted into the comparator to create an inhibit function when the vending should be prohibited. However, once the vend cycle begins, it seizes control and prevents a malfunction resulting from any change in conditions which occur during the vend cycle.

For a more complete description, reference is made to the following specification and drawings of a preferred embodiment of the invention, wherein:

FIG. 1 is a block diagram of the coin changer control circuit;

FIG. 2 is a diagram of the logic input control circuit for each of three exemplary coins;

FIGS. 3-5 are a diagram of the system logic;

FIG. 6 is a layout diagram of FIGS. 2-5 which may be joined in the indicated manner in order to provide a complete and understandable circuit; and

FIG. 7 is a timing chart which illustrates how the circuit of FIGS. 2-5 operates.

The principle assemblies of FIG. 1 are a coin box 20, a master clock 21, a coin monetary value controlled circuit 22, and system logic 23.

The coin box 20 may be essentially any well-known coin sorting, slug rejecting device adapted to give a coin value identifying switch closure responsive to the presence of a deposited coin. The currently used devices generally have a funnel-like opening 24 for receiving coins or tokens of all usable values. Inside the box 20, the coins are sorted according to their monetary value, validated, and slugs are rejected. Thereafter, the coins are placed in escrow until either a demanded product is delivered or the coins are returned to the customer. During the vend cycle, the escrow is collected. If the vend cycle is not completed, the escrow is returned to the customer.

The master clock 21 includes a series of electronic gates or switching circuits which respond to the cyclic polarity changes of commercial A. C. power. In the United States, these plarity changes occur at a frequency of 60 cycles per second; however, the system is equally adaptable to be used with other forms of commercial power.

The coin monetary value controlled circuits 22 comprise a plurality of coin actuated switches 31 located inside the coin box 20 and adapted to change a marking potential from a first to a second lead as the indicated coin drops through the chute. The symbology is that a normal ground marking normally appears on leads marked 5, 10, and 25, cents respectively. When a coin is present in the chute, the ground marking is switched from these leads to the leads marked 5, 10 and 25 cents respectively. Thus, for example, in the normal state, a ground marking is applied through contacts 32 to a 25 cents lead 33. When a quarter is in the coin chute 35, contacts 32 open and contacts 36 close to apply a ground marking to the 25 cents lead 37.

The 25 cents logic circuit 38 responds to the marking on 25 cents lead 37 by applying a suitable enabling signal to one input of an OR gate 39 feeding an AND gate 40. Every time that the A. C. commercial power changes polarity to a first half cycle at the commercial power line 41, the AND gate 40 conducts to gate out a pulse on wire 43 to the system logic circuit 23 and to feed back a pulse via wires 44, 45 to the individual 10 and 25 cents logic circuits 48, 38. (There is no need to feed back a signal to the 5 cents logic 47 since there is only one pulse for this value.) After the logic circuit 38 has counted five fedback pulses, meaning five 5 cents units, it removes the enabling signal from OR gate 39, thus terminating the transmission of coin pulses over lead 43.

In a similar manner, when a dime is in chute 49, the 10 cents logic circuit 48 controls gate 39 to gate out two (two 5 cents unit) coin pulses over lead 43 to the system logic.

The system logic circuit 23 contains a register 55, a push button controlled input circuit 56, a comparator 57, and a driver 58 for operating the mechanical controls 59 of the vending machine.

The mechanical vending machine has a plurality of push buttons 61 which selectively close contacts to mark leads at 65 which are cross-wired at a patch panel 62 to any desires monetary value input terminal 63. The term "push buttons" includes all vending machine selection actuators, such as rods, shafts, levers, and the like which are capable of selecting a product. A coder 64 converts the terminal price into a binary form matching the binary form of signals stored in register 55. Thus the register 55 and coder 64 give essentially the same output for the same monetary value.

If the comparator finds that less than the necessary amount of money has been deposited, there is no vend cycle, and the customer may either operate a coin return lever to return the escrowed coins or deposit additional coins until the output of register 55 matches the price indicated by the coder 64.

If the comparator 57 finds that at least the required purchase price has been deposited in escrow, it transmits a signal toward the driver 58. However, before this transmitted signal can reach the driver 58, it must first pass through check points in the comparator 57, which preclude signal passage if (a) more than a certain maximum number of coins is required for the change, (b) the changer contains less than this maximum number, or (c) a coin is jammed in the coin box 20. If the comparator signal passes all of these check points, it is released to the driver 58, and the vending machine 59 operates. If the comparator signal does not reach the driver 58, the customer may operate the coin return lever (not shown) and obtain a refund of the escrowed coins.

The mechanical controls of the vending machine may (a) collect the escrow, (b) return the escrow, (c) vend the selected product, (d) lock the mechanical selection devices to insure a complete vend cycle, and (e) issue change. These mechanical control functions are already built into most vending machines, are performed in any suitable manner, and do not have to be further described herein.

The master clock 21 is found in the upper lefthand corner of FIG. 2. In greater detail, the commercial power line 41 is connected through voltage dropping resistors 70 to a band pass noise filter 71 which passes only the commercial power frequencies and rejects all other frequencies. The commerical power, passed by filter 71, is applied to two wave shaping gates 72, 73 having a feedback circuit 75 which gives a Schmidt trigger effect to drive the gates on and off. These gates produce an endless series of cyclically recurring pulses having a constant pulse repetition rate synchronized with the frequency of commercial power on line 41. The series of the pulses so produced appears at the output marked CK in FIGS. 2 and 7. The CK pulses are also fed to a phase inverter circuit 76 which provides a second series of inverted pulses marked CK in FIGS. 1 and 7. The delays in the phase inverter 76 are such that the CK pulses begin and terminate prior to the beginnings and terminations of the CK pulses. The repetition rate, shape and duration of each pulse in these two series are substantially the same.

By way of example, the generation of a coin pulse may be traced through the 25 cents logic section 38. However, it should also be understood that essentially the same pulse generation may be traced through the 10 cents logic section or through any other logic section (not shown) whigh might be provided, such as for 50, cents 100, cents or a token.

Normally, a 25 cents flip-flop stands on its "0" side responsive to a coin ground marking normally applied through contacts 32. When a 25 cents coin is deposited in coin box 20, contacts 32 open, and contacts 36 close. The ground marking now causes an output from the "1" side of the flip-flop. This "1" signal may pass through a noise filter 81 designed to reject all non-standard pulse forms or other noise.

An inhibit signal is applied to a special inhibit wire 82 throughout the mechanical parts of the vend cycle so that coins dropped into the coin box during the mechanical operations cannot affect the vending function, (the machine returns them to the customer). However, if the coins are dropped at a time when the machine is not going through the mechanical portions of a vending cycle, there is a low polarity signal on wire 82 and a coincidence at the input of an AND gate 83.

The AND gate 83 conducts responsive to the presence of a quarter and applies a signal to an OR gate 84, and, in turn, an OR gate 85 to energize a JAM lead 86. As long as the coin is present in the coin box 20, the jam signal will continue to appear on the lead 86. During normal operation, the coin drops into the escrow hopper, and the jam signal disappears from the wire 86 in due course. The output of AND gate 83 is also applied to set a flip-flop 90, to energize its Q terminal as a memory that a 25 cents coin has been deposited.

From an inspection of FIG. 7, the coin memory (90Q output) is a randomly occurring event which can happen at any time in a clock cycle, as is indicated by a cross-hatched area 91. Therefore, this randomly occurring event must be synchronized with the clock cycle. Accordingly, the coin memory signal 90Q is fed through OR gate 92 to an AND gate 93 which conducts when the next clock pulse CK occurs and energizes gate 97, as indicated at 95 in FIG. 7. (It should be apparent that the 10 cents memory 94 feeds the OR gate 92 in a similar manner.)

The output of AND gate 93 feeds through OR gate 96 to trigger a counter-input stage 98, which follows the trailing edge of the pulse, as indicated at 99 in FIG. 7. The start gate stage 98 switches on to give an "A" output. Thereafter, it remains on for the duration of the coin pulsing caused by the deposited coin. When stage 98 is "on" the counter 100 is enabled to count the coin pulses appearing at its input 101.

The output from stage 98 is fed back to inhibit gate 97 and prevent any further effect responsive to a clock pulse CK. The output of start gate stage 98 is also applied to an AND gate 102 and to gate 103 leading to the gate 85 and the JAM conductor. Hence, as long as the coin pulses are being transmitted over lead 43, the system behaves as if there were a jammed coin.

When the next CK pulse 104 occurs (FIG. 7), AND gate 102 conducts to energize an input of OR gate 105 and thereby send a coin pulse over the wire 43. The same coin pulse is also fed back to input 101 where the counter 100 is driven one step. The output of counter 100 is described by the following truth table:

COUNT OUTPUTS: STATE A B C D NORMAL 0 0 0 0

start 1 0 0 0 1 1 1 0 0 2 1 0 1 0 3 1 1 1 0 4 1 0 0 1

normal 0 0 0 0

as can be seen, the "1" output at A occurs when start gate 96 first conducts, and it remains throughout all five counting conditions.

Responsive to the first coin pulse fed back to input 101 (as indicated 107, FIG. 7), the B output is marked. However, there is no effect at gate 108 because gate 109 is not marked from the 10 cents logic memory circuit 94. Therefore, the next or second CK appears at AND gate 102 and causes a second coin pulse (indicated at 110 in FIG. 7) to be fed out over wire 43 and fed back to input 101. From the above truth table, the C output is marked, but it is vacant, and there is no effect. On the next or third coin pulse, wire 43 is marked and a signal is fed back to terminal 101, which causes terminals B and C to be marked, again, without effect. On the next or fourth pulse, as indicated at 111, FIG. 7, the terminal D is marked.

Responsive to a "1" output at stage D of the counter 100, one terminal of a terminator AND gate 115 is marked. The other terminal of gate 115 is marked responsive to the output Q of the 25 cents memory flip-flop 90, the marking being extended via a steering gate 116. Thus, the terminator gate 115 conducts and a signal 120 (FIG. 7) is fed through OR gate 117, AND gate 96, to the stage 98. The output of gate 96 is an enabling signal which will momentarily replace the signal Q from the output of the 25 cents memory 90.

The signal 120 from gate 117 also feeds through gate 121 to reset the memories 90, 94 and thereby remove the signal from the output terminal Q, as indicated at 122, (FIG. 7). It is important to recall that the counter 100 follows the trailing edge of the gated out coin pulse. Therefore, by the time the Q signal disappears from the 25 cents memory 90, it will already have been too late to affect the outgoing pulse. Meanwhile, OR gate 117 is feeding back a signal to the OR gate 116 and thereby holding a signal on the lower input of terminator gate 115. Thus, gate 115 remains on, in simulation of the 25 cents memory Q signal, as indicated at 120 (FIG. 7).

When the next and fifth coin pulse 124 (FIG. 7) appears on lead 43, the D output of counter 100 disappears, as indicated in the above truth table. When the D signal disappears, gates 115, 117, and 116 turn off. The gate 96 also turns off to remove the enable signal from stage 98 and thus terminate the A signal, as indicated at 125 (FIG. 7).

Responsive to the end of the A signal at stage 98, the gate 102 turns off. Thereafter, no further clock pulses CK can reach the coin pulse lead 43 or feedback to the counter input terminal 101. The circuit of FIG. 2 is now normal and waiting for the next operation. If the coin has not yet dropped through the coin box 20 (FIG. 1), a signal remains on JAM lead 86.

If 5 cents is deposited, flip-flop 50 operates to send one pulse through gate 105 to coin pulse lead 43. If 10 cents is deposited, two pulses are sent. If 25 cents is deposited, five pulses are sent. In a similar manner, any number of pulses up to $1.55 (or 31 pulses) may be sent over wire 43 responsive to the cumulative value of a multiple coin deposit. Hence, the system logic 23 (FIGS. 3-5) knows the total value of all coins deposited in coin box 20.

The coin pulses on lead 43 arrive at the register 140 (FIG. 3). The principal elements in the register 140 are a pair of integrated circuits 141, 142 connected together to function as a bi-directional counter which may count up to add or count down to subtract. If input pulse signals appear at input terminal 143, the counters 141, 142 count up. If they appear at input terminal 144, the counters 141, 142 count down.

Means are provided for driving the counter up to store the cumulative value of deposited coins. More particularly, when the counter 141 counts up, each step doubles the indicated value; therefore, the counter 141 outputs A'-D' represent 5, 10, 20, and 40, cents respectively. For example, a 15 cents deposit is registered when there are outputs at A' and B'. Since the foregoing description has been made under the assumption that 25 cents was deposited, there should now be an output signal at terminals A' and C' indicating 5 and 20 cents.

When more coins having a cumulative value of more than 75 cents are deposited, the counter 141 is full and the next coin pulse at terminal 143 causes a signal to be sent over a "carry" lead 145 to set a flip-flop 142 and thereby mark its output terminal Q' to store a memory that 80 cents has been accumulated responsive to many coins deposited in coin box 20 (for example, three quarters and one nickel). Thereafter, the counter 141 is at the normal zero count condition, and it may again count an additional 75 cents (i.e., a total of $1.55) before it again reaches capacity. At this time, there is a coincidence of signals at the "carry" output 145 and at the Q' terminal of flip-flop 142. Responsive thereto, gate 147 conducts to inhibit an AND gate 146 and thereby prevent the registration of any more pulse signals. This inhibition prevents the registration of more coins, which would cause the counter to fold back upon itself and, in effect, forget the first $1.55. Simultaneously, the signal from gate 147 may return any additional coins dropped into the machine. An inhibit terminal 82 is marked during the actual vend operation to preclude further control of the coin pulse counter 141 at that time.

Means are provided for driving the register in a down circuit to subtract the monetary value of coins issued as change. It should be recalled that this description relates to the electrical controls. The physical issuance of the coins is under the control of the mechanical changer, as described below.

A coin pulse out switch circuit 151 is controlled by contacts 152 responsive to the mechanical issuance of each coin (a nickel) as change is made. Thus, responsive to each nickel issued in change, a coin out pulse signal is generated at contacts 152 and fed through noise filter 153 and gate 154 to a down count input terminal 144. This pulse drives the counter 141 in a reverse direction to reduce the stored cumulative monetary value by 5 cents per pulse. If the down count crosses the 80 to 75 cents zone, a signal is sent over the "borrow" lead 155 to reset flip-flop 142, thereby removing the memory of 80 cents and resetting the counter 141 to enable it to again count down.

For example, a person buying a product having a purchase price of 90 cents might deposit four quarters. The counter 141 originally filled when it counted up to 75 cents. Responsive to the next coin pulse (meaning 80 cents) appearing on lead 43, flip-flop 142 is set to give an 80 cents cumulative deposit which is indication by a high polarity signal at terminal Q'. The next four pulses cause counter 141 to count up and mark terminal C' to indicate a deposit of an additional 20 cents. The combination of an 80 cents signal at terminal Q' and a 20 cents signal at terminal C' equals $1.00 deposited. When the changer issues two nickels in change, it simultaneously operates contacts 152 and pulses terminal 144 twice. The counter 141 counts down two. Now there are signals at terminals B' and Q' indicating 10 cents + 80 cents or a total of 90 cents (i. e., the purchase price).

As another example, if the purchase price is 75 cents and eight dimes are deposited, the same process is followed. Terminal Q' is marked to indicate a total deposit of 80 cents. One nickel is issued in change, and a pulse is applied to the terminal 144 to cause counter 141 to count down one step. A "borrow" signal appears on lead 155 to reset the flip-flop 142 to normal, thereby canceling the 80 cents memory signal at terminal Q'. Simultaneously, the counter 141 is reset to mark terminals A', B', C', D' for indicating a total deposit of 5 cents + 10 cents + 20 cents + 40 cents or 75 cents, the purchase price.

It should now be apparent how the register stores signals representing the net total amount of money stored in the coin box 20 (i. e., the escrowed coins less any change returned to the customer).

Means are provided for indicating the purchase price of the selected product. In greater detail, each push button on the vending machine operates a switch that electrically marks a wire 61 which identifies the customer's selection. A patch-board or other cross-wired field 62 is optionally interconnected so that these signal leads 61 energize one of the indidual price terminals 164. Thus, to change a price, it is only necessary to change the jumper connection across the field 62.

For example, a first push button on the vending machine may demand a product priced at 25 cents, in which case wire 160 is connected through field 62 to the 25 cents terminal 162. A last push button may select a product priced 50 cents, in which case wire 161 is connected through field 62 to the 50 cents terminal 163. In like manner, every push button is connected to electrically energize a terminal indicating the price of the product selected when the push button is operated.

The digital price terminals 164 are coded into binary signals by the gates 64. Thus, for example, if a path is traced from the 50 cents terminal 163 through the gates 64, it is found that the output price terminals P10 cents and P40 cents are simultaneously energized via gates 166-168. Likewise, a path may be traced from any other price terminal 164 through the coder 64 to similar price leads which add to indicate the purchase price of the selected product.

A delay circuit 170 has built in time delays controlled by the clock pulses CK and CK. The delay persists long enough to allow all of the mechanical movement and resulting electrical signals associated with the push buttons to come to stabilize before there are any electrical effects upon the control circuit. Only thereafter does a signal appear on the lead 171. The gates 172, 173 are connected to detect push button caused price signals and to trigger the delay circuit 170 responsive to any price registration.

Means are provided for indicating whether the cumulative monetary value of escrowed coins at least equals or exceeds the purchase price of the selected product. In greater detail, the output of the register 140 (i. e., signals representing the cumulative value of deposited money held in escrow) and of the coder 64 (i. e., the price of the selected product) are compared at circuit 57.

The principal elements in the comparator circuit 57 are two four bit adders 175, 176 having parallel inputs 180 and parallel outputs 181. The nature of these four bit adders is such that if corresponding inputs are properly energized, a signal does not appear at the corresponding output, and a carry signal is transferred to the next stage. Thus, for example, if the 5 cents lead 182 is energized by counter 141 (showing a deposited coin), and if the P5 cents lead 183 is energized by the coder 64 (showing a price), there is agreement between the deposit and the price. No signal appears at the C5 cents change price lead 184, and a carry signal is transferred to the 10 cents stage in the counter 175. Thereafter, the 10 cents stage may function in a similar manner. Hence, a carry signal is propagated from left to right through the successive stages of counter 175, 176.

As long as the compared leads from register 141 and coder 64 have the same relative signal potentials thereon, there are no outputs on the change leads 181, and the carry signal continues to be propagated from the left, stage to stage, toward the counter output terminal 185.

Obviously, therefore, the comparator circuit 57 may encounter one of three conditions during the vend cycle: (a) the cumulative value of the deposited coins is insufficient to pay the price of the selected article; (b) the cumulative deposited value exceeds the price of the selected article; or (c) the cumulative deposited value exactly equals the price of the selected article.

If the deposited money is insufficient to pay for the selected product, the propagated carry signal does not reach output terminal 185. Nothing further happens. The customer either deposits more money or operates a coin return mechanism (not shown) in the usual manner.

If the purchase price is less than the deposited money, change is required. A signal appears on one or more of the leads 181, according to the amount of change required. For example, signals on wires C5 cents and C10 cents mean that a change of three nickels is required.

However, it is important that the changer machine have enough coins stored in its chute to give the required change. Therefore, the vending machine is arranged to preclude vending if the amount of change required is more than four nickels. This amount (a 20 cents value) is selected since it is the largest amount which is ever required if the customer deposits coins having the closest cumulative value possible. That is, if he uses the largest coin, a quarter, to add the least value, 5 cents, to the escrow, he is entitled to 20 cents change. Accordingly, the coin chute locks up and an "exact change" light lights when less than five nickels are available for change at the start of the vend cycle. Hence, the coins in the chute for making change is always sufficient to make the change if the "exact change" light is out.

Means are provided for electrically ordering the issuance of change after all of the change-making criteria has been met. More particularly, the gates 190 make the decision as to whether four or less coins are required to make the required change. If there is a monetary excess of escrowed coins, as compared to the indicated price, the excess is indicated by potentials on the change leads 181. Thus, five cents in monetary excess of the escrow over the price causes a potential to appear on the C5 cents lead 184. A ten cent excess causes a potential on the C10 cents lead, etc.

Next, the flip-flop 191 normally has a high polarity output unless the number of nickels in the changer chute falls below the required minimum number (i. e., five nickels in the above example). If there are less than five nickels in the changer chute, switch 192 operates. The output of flip-flop 191 reverses to give a potential of a low polarity at its output. This output of flip-flop 191 is fed through a noise filter 193 to an AND gate 194. Thus, gate 194 conducts only if there is a low polarity voltage, meaning that the changer chute does not have a minimum number of coins required to make change if the maximum allowable amount of change is required. The upper input of gate 194 is an inhibit terminal which is marked when the vend cycle is in process. When the AND gate 194 conducts, a gate 194a also conducts and an electronic switch 194b turns on to light a changer empty lamp meaning that exact change is required. If the vend cycle is in process, the upper input to AND gate 194 is at a high polarity to inhibit and prevent it from being energized. Thus, after a vend cycle once starts, coins will continue to be issued even if the number of coins in the changer chute falls below the allowable minimum number of five. This way, there always are enough stored coins to make the correct change.

If the AND gate 194 is off to indicate that there are a sufficient number of coins or that a vend cycle is in progress, a high polarity inhibit signal appears at the upper input of the AND gate 195. If there is a 5 cents or a 10 cents monetary excess in the escrowed deposit, the OR gate 196 conducts. The output of gate 196 feeds through OR gate 197, but not through gate 195 which is inhibited by flip-flop 191 and gate 194. Hence, a vend cycle may be started. If the escrow has a monetary value requiring four nickels, the C20 cents lead is energized, and the lower input to AND gate 200 is energized. The gate 200 does not conduct unless the upper input is also energized, meaning that more than four nickels are required to make change. Hence, a vend cycle may be started if the escrowed monetary value excess is 5, 10, 15, or 20 cents because no signal may then pass through gates 195 or 200.

If more than four nickels are required to make change, the start of a vend cycle is inhibited. In greater detail, AND gate 200 conducts if the lower input is marked to indicate a necessity for a change of C20 cents, and if the upper input is marked to indicate that an additional 5, 10 or 15 cents is required. Responsive to the output of AND gate 200, the OR gate 198 conducts and the inverter 199 gives a low polarity start of vend inhibiting signal on lead 201. If change of 40 cents or of 80 cents is indicated, the OR gate 202 conducts with a similar result.

Upon reflection, it should be apparent that the lead 201 has a low polarity marking if (a) the changer chute is empty and if 5, 10, 15 or 20 cents change is required because AND gate 195 then conducts or (b) if more than 20 cents change is indicated because AND gate 200 or OR gate 202 conducts. This low polarity marking prevents the start of a vend cycle. On the other hand, the lead 201 has a high polarity marking if less than 20 cents change is required and if at least four nickels are in the changer chute available for making the change. This high polarity marking is a start of vend enable signal.

As each of the proper number of coins are issued as change, the register 140 counts down to the price of the selected product. When parity is reached, there is a valid comparison in the four bit adders 175, 176, there are no further change required output signals at 181, and the carry signal in the adders 175, 176 propagates to the validation control section 204 of the four bit adder 176.

A number of prequisite validation signals must be present at the input to section 204 in order to start a vend cycle. In greater detail, if any coin is still in the coin box 20, there is a signal on the JAM lead 86 to prevent further propagation of the carry signal through the four bit adder 176. Since the coin travels at a mechanical speed and the carry signal at electronic speed, the JAM signal normally persists for a time. When the coin falls clear of the coin box 20, the signal on the JAM lead 86 changes polarity to enable the carry pulse to propagate to the next section of the four bit adder 176.

Means are provided for verifying the equality between the cumulative monetary value of the escrowed coins and the indicated purchase price of the demanded product. More specifically, if the change has not been properly issued or if there is a difference between the cumulative monetary value of coins in escrow and the purchase price, the potential on wire 201 has a low polarity marking to prevent the propagation of the carry signal through the four bit adders 175, 176. As the change is issued, there comes a time when the escrowed value and the purchase price are equal. The potential on wire 201 becomes a high polarity and the carry signal is allowed to propagate through the adder 176 to the next stage.

Means are provided for allowing the mechanical or electrical disturbances to subside after push button operations and before the release of the carry signal in the adder. More particularly, the potential on wire 171 is a low polarity during this delay period as measured by the circuit 170.

This timing delay is seen in FIG. 7. The OR gates 172, 173 are detector devices which become conductive when a push button is operated to transmit a signal through the gates 64. The push button operation occurs at random during a clock cycle, as indicated by the cross-hatch time window 208 (FIG. 7). When a clock pulse CK appears simultaneously with the push button caused electrical signal 208, the flip-flop 206 operates. As indicated at 209 (FIG. 7), this operation window is reduced to the width of the clock pulse CK appearing immediately after the push button operation and marking the flip-flop 206. The output from flip-flop 206 enables the flip-flop 207 to operate responsive to the next clock pulse CK. Note that clock pulse CK always goes to a low polarity before clock pulse CK goes to a high polarity. Thus, the minimum time T (FIG. 7) required to operate the flip-flop 207 is the width of a clock pulse CK. If the gates 173 or 206 become conductive earlier or later during their respective operate windows 208, 209, the time period T will be longer or shorter, respectively. The gate 173 remains on until it is reset at its terminal R, at the end of the cycle.

After a delay period expires, all disturbances caused by operation of the push button will have subsided. Therefore, the electronic circuit may operate dependably, and wire 171 changes to a high polarity. The carry signal propagates through the last stage in the four bit adder and is released on the wire 185. Noise filter 205 prevents noise from simulating a push button price-indicating signal.

Means are provided for starting the vend cycle after all of the validation signals are in their proper phase. In greater detail, the carry signal appears at the terminal 185 when all of the validation signals in section 204 are in their proper phase to enable a start of the vend cycle. This carry signal at the terminal 185 causes an inverter 210 to operate a flip-flop circuit 211 via noise filter 212. The high polarity output, at "RUN" terminal 213, of flip-flop 211 is a memory that the vending cycle has begun, which precludes a change during the cycle from having an effect before the termination of the vending operation. Filter 212 also eliminates a response to ripple signals which may occur as the four bit adder 176 operates, as when change is given, for example.

The high polarity "RUN" marking at 213 is returned to the upper input of AND gate 194, thereby inhibiting it and precluding any control effects if the number of coins in the changer chute fall to less than the maximum allowable change. This control is provided because the number of coins may fall below this maximum as change is issued during this vend cycle. Yet another result of the operation of flip-flop 211 is an energization of OR gate 214 and electronic switch 215. The output of switch 215 causes (a) a push button controlled solenoid 216 to lock so that the selection cannot be changed during a vend cycle, (b) the collect solenoid 217 to operate and collect the escrowed coin, and (c) a peg count device 218 to operate for keeping a record of the number of times that the vending machine operates.

To prevent a catastrophic failure wherein the vending machine locks in the coin refund condition and empties the entire contents of its changer, three redundant circuits are provided. Since, mathematically speaking, joint probabilities are a multiplication function, the chances for three simultaneous failures are very small.

In greater detail, the marking potential on wire 185 is a low polarity if there are insufficient funds in escrow and a high polarity if the funds are either equal to or greater than the purchase price. Thus, if there is a low polarity, the vending machine will not go into a vend cycle. If there is a high polarity, the vending machine must next know whether to issue change. Thus, the "RUN" output of flip-flop 211 feeds back to the input CO of the four bit adder 175. This fed back input subtracts one count in the comparator circuit so that the carry signal on wire 185 changes from a high polarity to a low polarity if the escrow exactly equals the purchase price. However, if the coin changer must be operated, the polarity on wire 185 does not change when the one pulse applied to the input CO is subtracted from the stored total. (Note that once the "RUN" memory flip-flop 211 is operated, the carry pulse is no longer required on wire 185 in order to drive the vending machine through its vend cycle.)

Means are provided for commanding the issuance of change when the polarity on wire 185 does not change after one pulse is subtracted from the stored total. More specifically, the release of the carry pulse energizes the wire 185 and marks the upper input of an AND gate 220. The next clock pulse CK causes gate 220 to conduct if the polarity on wire 185 does not change to indicate an exact change condition. Thus, pulse CK sets the flip-flop 221. The clock pulse CK is also used for this pulse release control function to be certain that the pulse will have a standard length and to prevent a situation where a function begins after the start of a clock period, thereby reducing duration time of an otherwise standard pulse.

A moment later flip-flop 211 energizes the lower gate 222 in flip-flop 221. A low polarity signal appears at the input of the AND gate 223 which becomes conductive. The gate 223 marks the lower input of the AND gate 224. The high polarity marking of the carry pulse is present on wire 185 if change is required, because the wire 185 did not change polarity responsive to the one signal fed back to input terminal CO. If these three gates, 222, 223, and 224 function properly during this time interval while the carry pulse has a high polarity, an inverter 225 operates an electronic switch 226 to drive a coin refund motor 227. The motor repeatedly operates a slide which issues the refund coins, one at a time. Each issued coin is indicated by a pulse formed at contacts 152 (FIG. 3).

The register 141 counts down responsive to the issued coin pulses until the net monetary value of the coins in escrow less the value of coins refunded exactly equals the price of the vended product. At that time, the carry signal disappears from lead 185. The high polarity signal disappears from the upper input of the AND gate 224, switch 226 turns off and no more coins are refunded. Of course, the circuit is arranged to issue a coin responsive to the pulse which was subtracted by the input signal applied at input CO. During the refund cycle, a feedback signal at 229 provides an interlock to prevent an incomplete coin refund cycle and to insure that each refunded coin is actually delivered to the customer.

When the net monetary value stored in counter 141, 142 and the price indicated by the push button signals in adder 175, 176 reach equality, wire 185 switches to a low polarity signal to mark the lower input of an AND gate 230. If the run flip-flop 211 has switched to its off-normal state, the upper input of gate 230 is also marked. The AND gate 230 conducts, electronic switch 231 operates, and the vend motor 232 runs to deliver the product to the customer.

Means are provided for returning any coins deposited either during a vend cycle or if the power fails. More particularly, a normally operated magnet CREM causes an automatic coin refund after it releases. It releases upon power failure. It also releases during a vend cycle when flip-flop 211 operates switch 238 via gates 235 and 239. Thus, a fraudulent person cannot pull the power cord and obtain both a vended product and a refund of his money.

After the vend cycle is completed and the selected product has been delivered to the customer, a pulse signal appears at 236. For the duration of the pulse at terminal 236, there is a coincidence at the input of gate 237 while gate 235 is on. Among other things, the gate 235 prevents noise at terminal 236 from simulating an end of vend signal. Thereafter, an output from gate 237 causes a delay in circuit 240 which operates through a cycle, substantially the same as described below in connection with delay circuit 170. Then, a reset signal appears at output 241.

Responsive to the signal at output 241, gates 242, 243 conduct to reset the "RUN" flip-flop 211, the counters 141, 142, and the push button detector gate 173. A signal is fed over the clear lead CL to the circuit of FIG. 2, where the flip-flops 90, 94 and counters 98, 100 are reset. When flip-flop 211 resets, it deenergizes the "RUN" bus 213 and removes the enable signal. Gate 243 also marks the inhibit conductor 82 to prevent circuit changes after start of the vend RUN cycle, as marked by flip-flop 211.

Means are provided for delaying the operation of the circuit for a predetermined period of time after power is first turned on. This delay enables stability to be achieved before the system operates. That is, the capacitor 247 changes over a discrete period of time after power is first turned on. After the change reaches a predetermined potential, the gate 242 is energized to reset and hold normal circuit conditions. Thus, stability is assured.

Means are provided for refunding coins from the escrow at the customer's command. That is, contacts 250 are operated by a coin return switch on the vending machine. If the customer operates the return switch, the refund flip-flop 151 switches to mark the upper input to the AND gate 252. The lower input of this gate will also have an enabling marking, unless the "RUN" 211 has been switched. This way, the vending machine cannot be defrauded by a quick operation of the refund lever after the vend cycle has begun and the enabling potential has disappeared from gate 252. The output of the gate 252 is fed through a gate 253 to turn on an electronic switch 254 and thereby return the deposited coins being held in escrow.

From the foregoing description, it should be apparent that the invention provides a relatively simple, low cost vending machine control circuit which may be built with either discrete components or on an integrated chip, depending upon the anticipated volume of production. Moreover, the cross-wiring at patching panel 62 enables a quick and easy change of prices. Also, various modification may be made in the circuit according to the needs of any particular vending machine. Therefore, the appended claims are to be construed to cover all equivalent structures falling within the scope and the spirit of the invention.

Claims

I claim:

1. A control circuit for a vending machine comprising separate logic input control means for each coin of a different monetary value accepted by the machine, system clock means for generating cyclically recurring clock pulses, means responsive to each of said logic input control circuit means for gating out a train of clock pulses having a number of pulses selected to represent the monetary value of each deposited coin, register means for storing each pulse in the train of the gated coin representing pulses, and means for comparing the cumulative total of the stored train of pulses with signals representing the price of a selected product to enable or inhibit the vending cycle.

2. The control circuit of claim 1 and means responsive to the detection of predetermined vending machine conditions for inserting an inhibit signal into the comparing means to create an inhibit function.

3. The control circuit of claim 1 and means responsive to the start of a vend cycle for precluding any control operation responsive to changing conditions occurring during the vend cycle.

4. The control circuit of claim 1 and means responsive to the cyclic polarity changes of the alternating current of a commercial power source for generating said clock pulses.

5. The control circuit of claim 1 wherein said register is a bidirectional counter adapted to count up or to count down, means responsive to each of said coin pulses for driving said counter to count up, means for refunding coins responsive to said comparing means indicating a surplus of monetary value in escrowed coins as compared to the price of said selected product, means responsive to each coin refunded by said refunding means for driving said counter to count down, and means responsive to said comparing means during said count down finding equality of net monetary value of escrowed coins and said price for terminating the issuance of the refunded coins.

6. The control circuit of claim 5 wherein said refunding means comprises means responsive to said comparing means indicating said surplus of monetary value of escrowed coins for driving said counter to count down one initial pulse, and means responsive to a contained detection of said surplus of monetary value after the count down of said initial pulse for commanding the start of said refund.

7. The control circuit of claim 1 and a plurality of leads individually marked responsive to the selection of a vendable product, and a cross-wired field for connecting said individually marked leads to price indicating terminals.

8. The control circuit of claim 7 wherein said comparing means comprises an adder circuit having parallel inputs energized from said register means and from said price indicating terminals, and means for giving an output signal from said comparing means to command said vending machine to deliver a selected product when corresponding ones of said parallel leads have the same relative markings.

9. The control circuit of claim 8 wherein said comparing means has a validation section, and means responsive to predetermined vending machine conditions for inserting inhibiting markings on selected ones of said parallel inputs for inhibiting said vending command signal.

10. The control circuit of claim 9 wherein said comparing means comprise a four bit adder and said command signal is a carry signal passed from stage to stage through said adder responsive to parity at the parallel inputs.

11. A vending machine having a vend cycle beginning with a detection of escrowed money equal to or greater than the price of a selected article and ending with the delivery of selected goods or services and any required change, said vending machine comprising means for giving a coin value identifying switch closure responsive to the presence of each deposited coin, means for placing the deposited coins in escrow until either a selected product is delivered or the coins are returned to the customer, means responsive to the end of a vend cycle for collecting the escrowed coins, means for returning the escrowed coins to the customer at his command, master clock means for generating a series of cyclically recurring pulses responsive to the cyclic polarity changes of commercial A.C. power, electronic control means comprising a sequencer jointly responsive to said clock and a selection of said product for commanding the vending machine to undertake its entire vend cycle responsive to the output of said sequencer.

12. The vending machine of claim 11 and comparator means for comparing the monetary value of the coins in escrow with the price of said selected product, and means responsive to the comparator means finding that less than the necessary amount of money has been deposited for precluding the start of the vend cycle, and means responsive to the comparator finding that more than the necessary amount of money has been deposited for returning change until the escrowed coins match the price indicated for the selected product.

13. The vending machine of claim 12 wherein said comparator comprises inhibit means which precludes a passage of said vend start signal, means for operating said inhibit means responsive to detection of conditions where more than a certain maximum number of coins is required for the change, and where the changer contains less than this maximum number, and means for operating said inhibit means when a coin is jammed in the coin box.

14. The vending machine of claim 11 and counter means responsive to each deposited coin for storing signals generated by said clock means which represent the monetary value of said coin, means responsive to said deposited coin for driving the counter up to store a cumulative value of clock pulses representing the value of deposited coins, means responsive to said counter storing more than the indicated price of the selected product for issuing change, and means for driving the counter down to subtract the monetary value of each coin issued as change.

15. The vending machine of claim 14 and comparator means for verifying the equality between the cumulative monetary value of the escrowed coins less any issued change and the indicated purchase price of the selected product, and means for causing said commanded vending responsive to said comparator finding said equality.

16. The vending machine of claim 15 wherein the sequencer is part of said comparator means and comprises a multibit adder, means for inserting the output of said counter into said adder in parallel with pricing signals representing said selected product, said pricing signals being complementary to corresponding monetary signals from said counter, whereby said adder passes a carry signal when said price and said stored coin value are the same, and means responsive to a propagation of said carry signal through said adder for causing said command of vend signal.

17. The vending machine of claim 16 and means responsive to predetermined mechanical conditions in said vending machine for generating validation signals, and means for selectively inserting said generated validation signals in said adder for preventing the propagation of said carrying signal according to whether said mechanical conditions are such that said vending should not occur.

18. The vending machine of claim 17 and means for generating said command signal for starting the vend cycle after all of the validation signals are in their proper phase in said adder.

19. The vending machine of claim 18 and means responsive to said command signal for feeding back a signal for subtracting one coin value from the signals stored in said counter whereby the cumulative value of stored coins appears to be insufficient if no change is required, and means for commanding the issuance of change when the value stored in said counter does not change after said one value is subtracted from the stored total.